PWB

Printed wiring board (PWB) is a board used to mechanically support and electrically connect electronic components using conductive traces etched from copper and laminated onto a non-conductive substrate. The term PWB is often used interchangeably with printed circuit board (PCB); some sectors distinguish PWB to emphasize the network of interconnections rather than the circuit layout alone.

PWBs are manufactured through photolithographic etching or milling to create copper traces; drilled holes or vias for component leads; copper plating; and application of a solder mask and silkscreen. Substrate materials include epoxy-glass FR-4, phenolic FR-2, and polyimide for flexible PWBs. Copper weight commonly ranges from 0.5 to 2 oz/ft2, depending on current requirements. Finishes such as HASL, ENIG, or ENEPIG protect copper and facilitate soldering.

PWBs can be rigid, flexible, or rigid-flex. Rigid PWBs are used widely in consumer electronics; flexible PWBs are used when bending is required; rigid-flex combines both.

Design and production are guided by standards such as IPC-2221 for generic requirements and IPC-4101 for materials, as well as quality acceptance criteria in IPC-A-600 and related documents. PWBs are the core platform for mounting surface-mount or through-hole components; assembly methods include through-hole and surface-mount technology, and testing includes in-circuit and functional tests.

History: The concept emerged in the mid-20th century, evolving from early foil circuits to multilayer PWBs enabling higher component densities. In certain contexts the acronym PWB retains historical usage in aerospace, defense, and manufacturing supply chains.